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Related Concept Videos

Load-frequency control01:28

Load-frequency control

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Load-frequency control (LFC) is vital for maintaining power system stability, ensuring that frequency and power flows remain within acceptable limits during load changes. Turbine-governor control eliminates rotor accelerations and decelerations following load changes. However, a steady-state frequency error persists when the change in the turbine-governor reference setting is zero. In an interconnected power system, each area agrees to export or import a scheduled amount of power through...
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Time and frequency -Domain Interpretation of Phase-lag Control01:21

Time and frequency -Domain Interpretation of Phase-lag Control

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Phase-lag controllers are widely used in control systems to improve stability and reduce steady-state errors. A dimmer switch controlling the brightness of a light bulb serves as a practical example of phase-lag control, gradually adjusting the bulb's brightness. Mathematically, phase-lag control or low-pass filtering is represented when the factor 'a' is less than 1.
Phase-lag controllers do not place a pole at zero, but instead influence the steady-state error by amplifying any...
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Time-Domain Interpretation of PD Control01:07

Time-Domain Interpretation of PD Control

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Proportional-Derivative (PD) control is a widely used control method in various engineering systems to enhance stability and performance. In a system with only proportional control, common issues include high maximum overshoot and oscillation, observed in both the error signal and its rate of change. This behavior can be divided into three distinct phases: initial overshoot, subsequent undershoot, and gradual stabilization.
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Reducing Line Loss01:18

Reducing Line Loss

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In a three-phase circuit, line loss is an indicator of energy dissipated as heat due to the resistance of transmission lines. To address this, incorporating transformers into the system—a step-up transformer at the source and a step-down transformer at the load—is a strategic solution. Two three-phase transformers are introduced to improve this.
With a step-up transformer at the source, the voltage is increased, thereby reducing the current in the transmission lines since power loss...
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Linear Approximation in Frequency Domain01:26

Linear Approximation in Frequency Domain

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Linear systems are characterized by two main properties: superposition and homogeneity. Superposition allows the response to multiple inputs to be the sum of the responses to each individual input. Homogeneity ensures that scaling an input by a scalar results in the response being scaled by the same scalar.
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Cascaded Op Amps01:16

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Operational amplifiers (op-amps) are versatile electronic components that can be interconnected in a cascade - one after another in a linear sequence. This cascading is possible due to their infinite input resistance and zero output resistance, allowing them to maintain their input-output relationships even when connected in series.
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LED nonlinearity mitigation in LACO-OFDM optical communications based on adaptive predistortion and postdistortion

Mohammed Abd Elkarim, Moustafa H Aly, Hala M AbdelKader

    Applied Optics
    |October 6, 2021
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    Summary

    White light emitting diodes (WLEDs) offer efficient visible light communication (VLC). Predistortion and postdistortion techniques effectively compensate for LED nonlinear distortion, improving system performance with minimal signal-to-noise ratio penalty.

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    Area of Science:

    • Optical Communications
    • Signal Processing

    Background:

    • White light emitting diodes (WLEDs) are cost-effective optical sources for visible light communications (VLC).
    • LED nonlinear distortion significantly degrades VLC system performance.

    Purpose of the Study:

    • To investigate and compare three compensation techniques for mitigating LED nonlinearity in VLC systems.
    • To evaluate the effectiveness of predistortion and postdistortion methods on layered asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM).

    Main Methods:

    • Employed polynomial-based predistorters and postdistorters.
    • Utilized a look-up-table-based predistorter.
    • Analyzed performance using error vector magnitude (EVM) and bit error rate (BER) in an additive white Gaussian noise (AWGN) channel.

    Main Results:

    • Polynomial-based predistorters and postdistorters compensated for LED nonlinearity with an additional signal-to-noise ratio (SNR) of 0.25 dB at a BER of 10-3.
    • The look-up-table-based predistorter achieved the same BER with a lower SNR penalty compared to polynomial methods.

    Conclusions:

    • Predistortion and postdistortion techniques are effective in overcoming LED nonlinear behavior in VLC systems.
    • Look-up-table-based predistorters offer superior SNR efficiency for mitigating LED nonlinearity in ACO-OFDM based VLC.